Method of manufacturing hollow superconducting bodies

ABSTRACT

To make hollow stabilized superconductor bodies a core of two or more concentric materials is prepared, the center material having a low-melting point and the other being chemically, physically or biologically degradable. The core is introduced into a first stabilizing material; the thus constituted assembly is drawn; and the external surface of the drawn product is lined with superconducting elements. The subassembly thus developed is introduced into a second stabilizing material and the block thus formed is again drawn until it has the requisite dimensions and in such a manner that the two stabilizing materials will coldweld and embed the superconductor elements therein. Then the material or materials constituting the above-mentioned core are successively removed, the center core material by melting, or vaporization, and the outer core material by dissolving, or other physical, or chemical or biological methods.

United States Patent Matricon [54] METHOD OF MANUFACTURING HOLLOW SUPERCONDUCTING BODIES [72] Inventor: Marcel Matricon, Paris, France [73] Assignee: Thomson-CS1", Paris, France [22] Filed: Feb. 9, 1970 [2|] Appl. No.: 9,509

[30] Foreign Application Priority Data Feb. 13, 1969 France ..69034l7 [52] U.S.Cl. ..29/599,29/423, 29/DlG. ll, 174/D1G. .6 [51] Int. Cl. J'lolv 1l/00 [58] Field of Search ..29/599, 423, DIG. l1;

l74/D1G. 6, 126 R, 126 CP; 335/216 [56] References Cited UNITED STATES PATENTS 3,291,870 12/1966 Allison ..29/423 2,373,405 4/1945 Lowit.... ...29/423 X 2,499,977 3/1950 Scott ..29/423 'X 1 Feb. 15, 1972 Primary Examiner-John F. Campbell Assistant ExaminerDonald C. Reiley, lll Attorney-Flynn & Frishauf I 57] ABSTRACT To make hollow stabilized superconductor bodies a core of two or more concentn'c materials is prepared, the center material having a low-melting point and the other being I chemically, physically or biologically degradable. The core is introduced into a first stabilizing material; the thus constituted assembly is drawn; and the external surface of the drawn product is lined with superconducting elements. The subassembly thus developed is introduced into a second stabilizing material and the block thus formed is again drawn until it has the requisite dimensions and in such a manner that the two stabilizing materials will cold-weld and embed the superconductor elements therein. Then the material or materials constituting the above-mentioned core are successively removed, the center core material by melting, or vaporization, and the outer core material by dissolving, or other physical, or chemical or biological methods.

14 Claims, 8 Drawing Figures 1 METHOD OF MANUFACTURING Ho Low SUPERCONDUCTING BODIES The present invention relates to methods of manufacturing superconducting bodies and in particular to methods of making hollow stabilized superconducting bodies. Superconducting bodies lose their electrical resistivity when they are brought to a sufficiently low temperature, and retain this property of zero electrical resistance even when carrying heavy electrical currents. These bodies are therefore frequently used in the form of wires, cables or strips and shaped to form solenoids designed to generate high-strength magnetic fields which, because of their superconducting properties, can carry very heavy electrical currents without co'nsuming any power provided that appropriate cooling conditions are maintained.

However, if, dueto some random effect, a small portion of superconductor of which the solenoid is made losses its superconducting property and thus reverts to a finite, that is nonzero electrical resistance the extremely heavy current which is passing through the conductor resultsin the liberation of very considerable energy, in the form of heat, which'can have a .destructive effect. In order to guardagainst this'dan g er it is knownto stabilize" the superconductonthat is, to operate it side byside with a nonsuperconducting support which is both a very good thermal and electrical conductor, such as aluminum or copper for example, and ensuring that there is excellent heat-transferring contact between the superconductor and the support. If a portion of the superconductor accidentally transfers from the superconducting to the normal condition, the heavy current which is passing through the superconductor is shunted into the surrounding stabilizing support so that the resultant increase in temperature is very small, the current carried by the superconductor having been very substantially reduced with the result that the superconductor recovers its superconducting properties.

It is therefore an object of the present invention to provide a method to make a stabilized superconductor which is hollow, so that coolant fluid can be circulated through the superconductor, and inwhich the superconductor is in intimate contact with the stabilizing material.

Subject matter of the present invention: A core is first made which consists oftwo concentrically arranged materials. The center material is easily disposable in liquid or gaseous form at a temperature below that at which the superconductor, which will ultimately surround the material, would be damaged. The outer material of the core is disposable by physical, chemical,

. or biological means. A tube of stabilizing material then placed around the core. The tube of stabliziing material, with the core therein, is then drawn to a desired cross section, the outersurface of the stabilizing material preferably additionally being shaped to receive superconducting elements. The assembly of first stabilizing material, surrounding the core, and the superconductor is then introduced into a second stabilizing material fitting thereover. The composite assembly is then again drawn until the requisite dimension in cross-sectional shape is achieved, thetwo stabilizing materials cold welding together and, due to the pressure exerted by the internal core, becoming an intimate heatand electrical transfer contact with the superconducting material. Thereafter, the core' materials are eliminated, for example by melting out, by chemical action, or if the core material is otherwise degradable, for example biologically degradable, by removing the core material by such degradation.

The invention will be described by way of example with reference to the accompanying drawings, wherein:

7 FIG. I is a cross-sectional view of a composite body of wires of superconducting material in a stabilizing support;

FIG. 2 is a cross-sectional view of a hollow composite body;

FIG. 3 illustrates, in cross section, a composite body during one step of the method;

FIG. 4 is a cross-sectional view illustrating a further step in the method; I H

FIG. 5 is a cross-sectional view, to a greatly distorted scale, of a core or mandrel element;

FIG. 6 is a cross-sectional view of a subunit during a step of the method;

FIG. 7 is a cross-sectional view of a subunit to illustrate an alternative embodiment and method step; and

FIG. 8 is a crosssectional view of an embodiment of a final product resulting from the method.

FIG. 1 shows a composite body in which wires of superconducting material 1 are intimately incorporated into a stabliziing support 2 of copper or aluminum, for example.

Composite bodies can be made in the form of tubes (FIG. 2) so that they can be used at the same time to carry a refrigerant, thus simplifying the system.

In accordance with the invention, separate elements of large diameter and moderate length are assembled together as illustrated in FIG. 3. A first filler material forming an inner core portion 3, designed to be eliminated from'the final product, is surrounded by an outer core portion of a second filler material 4 likewise designed to be eliminatedfrom the final product. An internal tube 5 of stabilizing material, is surrounded by spaced wires 6 of superconductingmaterial, they may be simple superconductors or, may themselves be composites similar to those of FIG. 1. An external tube 7 of stabilizing material, similar to the material 5 (copper or aluminum for example) surrounds the outside. Next, and utilizing for example -the method ofsimultaneous drawing which forms the subject of French Pat. No. 1,460,032assigned to Compagnie Francaise Thomson Houston, the assembly system is drawn until the desired contours and dimensions are obtained. The result is shown in FIG. 4 where the component 8 is constituted by the former components 5 and 7 of FIG. 3, which have been welded together by the simultaneous drawing operation to become inseparable from one another. FIGS.3 and 4 are drawn to radically different scales.

Finally the filler materials 3 and 4 are removed using methods'which are appropriate to their particular nature or to i the substance of which they are made, that is either physical,

chemical or biological methods; For instance, if the material 3 is constituted by an easily meltable substance such asNa, K, Ga, Se, Rb, In, Cd, Sn, Cs, Tl, Pb, Bi, or alloys of these substances, or any alloys, or other substances having a low-melting point, or any organic or inorganic compound having a sufficiently low-melting temperature, then the assembly is heated to a convenient temperature in order to melt the'material 3 and permit it to run out, if necessary by applying pressure for the purpose by using a possibly inert gas at one side of the tubular system and a-vacuum at the other. The same method of removal by heating, is applicable and simplified, if the material 3 is easily vaporizable; a number of examples of materials which satisfy this condition are contained in the following table:

Temperature C. Temperature C.

melting boiling Aluminum bromide 97.5 263.3 Borontriiodide 43 210 Hexabromoethanc I48 2I0 Tetrabromomethane a 48.4

a 90.1 189.5 Silicontetraiodide 120.5 290 Siliconhexabromide 95 240 sncl, Poor 5s I Titaniumtetrabrornidc 39 230 Iodine I 13.7 184.35

facilitated by the fact that the extraction of the material 3 has left open a passage through which a suitable solvent can be introduced. For example, if the material 4 is aluminum, the solvent may be a soda solution.

The fact that right at the beginning of the operation two different materials, 3 and 4, both of which are intended ultimately to be eliminated, are provided, permits a certain margin of adjustment so that the system has plasticity characteristics which are desirable insofar as the simultaneous drawing operation is concerned.

Process steps: 7

The various stages of a manufacturing process in accordance with the invention will now be described by way of example. First of all, a core, or mandrel component of material 4 is made in the form shown in FIG. to form a solid component 9, of aluminum for example or of an alloy having a suitable plasticity. The component 9 is sealed off by a cap 10, of the same substance containing a filler tube 11. Next, the material 3 is introduced through tube 11 into cavity 12 within the body 9 in the liquid state, this by any appropriate means, vacuum and pressure for example; tube 11 is then suitably sealed off.

It is also possible to form solid material 3 to match the cavity 12; it is inserted, and then the cap 10 is welded to the body 9; the tube 11 is not needed.

It is further possible to insert the material 3 into the cavity 12 in the form of powder for example. In this case, it is frequently desirable to mix a major proportion of a powder whose thermal qualities are appropriate, with a small proportion of another powder whose thermal properties are just adequate but which confers upon the mixture the requisite plasticity properties for the drawing operation.

The cavity 12 of body 9, thus filled, can be subjected to several drawing passes; the drawing operation is halted when the length of the drawn rod enables it to be introduced into the tube 5 (FIG. 3). The subassembly of units 9 and 5 is then subjected to a number of additional drawing passes until it has obtained the form shown in FIG. 6 for example, the tube 5 being given a crenelated surface. At this time, the surface of the subassembly is lined by superconducting material. Wires of superconducting material 6, either plain superconductors or composite wires as seen in FIG. 1, are placed in grooves 13 and suitably retained therein. The system is then slid into the tube 7 (FIG. 3) which has been given the requisite form to fit thereover; the whole assembly is then drawn to simultaneously obtain the desired shape and cold-weld the stabilizing materials 5 and 7 together. The superconductor wires, plain or composite, will be firmly embedded in the now unitary stabilizing material and make intimate contact therewith. The circular symmetry at the stage shown in FIG. 6 may be retained, either because the rectangular form is not the final form required or because the cross-sectional shape is changed during later phases of the drawing operation. If a rectangular final form is required, a product of the kind shown in FIG. 8 is obtained in which the superconducting wires 6 are embedded in the stabilizer material 8. Many varient embodiments in the form of the crenelations, forming the grooves 13, are possible. FIG. 7 shows the superconducting wires 6 positioned in relation to one another by the interposition of strips 14, made of copper for example, which will also weld together with the inner and outer layers 5 and 7. Other fonns in which the superconducting elements, wires or composites, are arranged side by side without any intervening parts, may also be used.

When the final shape has been obtained, the extremities of the conductor produced are cutoff in order to eliminate the scrap ends deriving from the drawing of the base of the component 9 and that of the component 10 (FIG. 5). This bares the materials 3 and 4 and makes it possible to carry out the eliminating operations in respect of these materials, as described hereinbefore.

The foregoing description has been given purely by way of nonlimitative example although the invention includes other varient embodiments within its scope.

I claim:

' l. A method of manufacturing hollow stabilized superconducting bodies having a stabilizing material, and superconductive elements embedded in the stabilizing material, comprising:

preparing a core (3,4) having at least two concentrically located core portions, the inner core portion (3) being capable of becoming fluid at a temperature below that which damages the superconductive elements, and the outer one (4) being disposable by physical, chemical or biological methods;

introducing this core into a first stabilizing material (5 drawing the thus constituted subassembly;

lining the external surface of the subassembly obtained with superconducting elements (6);

introducing the lined subassembly thus developed into a second stabilizing material (7);

drawing the block thus formed until it has the requisite dimensions and simultaneously cold-welding of the two stabilizing materials taking place and embedding said superconducting elements into the cold-welded material, and

then subsequently eliminating the materials constituting the above-mentioned core (3, 4), by first rendering the inner core portion (3) fluid and eliminating the inner core portion and then attacking the outer core portion (4) from within to eliminate the outer core portion by physical, chemical or biological methods.

2. A method as claimed in claim 1, wherein the outer core portion is solid in form and containing a cavity (12) with an obturating device (10), the material of the inner core portion being contained in the cavity.

3. A method as claimed in claim 2, wherein the material of the inner core portion is introduced into the cavity in the first core portion, in solid form.

4. A method as claimed in claim 2, wherein the material of the inner core portion is introduced in molten condition into the cavity in the outer core portion.

5. A method as claimed in claim 2, wherein the material of the inner core portion is introduced into the cavity in the outer core portion, in the form of a powder or mixture of powders.

6. A method as claimed in claim 2, wherein the material of the inner core portion is' a gas entrapped in the cavity in the outer core portion at a pressure higher than the critical pressure so that the gas will be in liquid state.

7. A method as claimed in claim 2, wherein the material of the inner core portion introduced in the cavity in the outer core portion is a liquid such as water, mercury or the like.

8. A method as claimed in claim 2, wherein the material of the inner 'core portion introduced into the cavity in the outer core portion is an organic liquid.

9. A method as claimed in claim 1, wherein the drawing the of the subassembly composed of the core (3, 4), and the first stabilizing material (5), includes the formation, at its external surface, of grooves 13) for the locating of the superconducting elements.

10. A method as claimed in claim 1, wherein the subassembly composed of the core and the first stabilizing material, once it has been drawn comprises flat external surfaces upon which there are subsequently disposed the superconducting element (6) and intervening elements (14) of a material similar to the stabilizing material.

1 l. A method as claimed in claim 1, wherein the material of the inner core portion is eliminated by melting.

12. A method as claimed in claim 11, wherein the elimination of the material by melting, is assisted by the application of a gas pressure at one side, and the application of vacuum at the other.

13. A method as claimed in claim 1, wherein the material of the inner core portion is eliminated by vaporizing.

14. A method as claimed in claim 1, wherein the material of the outer core portion is eliminated by dissolving it in a solvent introduced into the space vacated by the elimination of the material of the inner core portion. 

2. A method as claimed in claim 1, wherein the outer core portion is solid in form and containing a cavity (12) with an obturating device (10), the material of the inner core portion being contained in the cavity.
 3. A method as claimed in claim 2, wherein the material of the inner core portion is introduced into the cavity in the first core portion, in solid form.
 4. A method as claimed in claim 2, wherein the material of the inner core portion is introduced in molten condition into the cavity in the outer core portion.
 5. A method as claimed in claim 2, wherein the material of the inner core portion is introduced into The cavity in the outer core portion, in the form of a powder or mixture of powders.
 6. A method as claimed in claim 2, wherein the material of the inner core portion is a gas entrapped in the cavity in the outer core portion at a pressure higher than the critical pressure so that the gas will be in liquid state.
 7. A method as claimed in claim 2, wherein the material of the inner core portion introduced in the cavity in the outer core portion is a liquid such as water, mercury or the like.
 8. A method as claimed in claim 2, wherein the material of the inner core portion introduced into the cavity in the outer core portion is an organic liquid.
 9. A method as claimed in claim 1, wherein the drawing the of the subassembly composed of the core (3, 4), and the first stabilizing material (5), includes the formation, at its external surface, of grooves (13) for the locating of the superconducting elements.
 10. A method as claimed in claim 1, wherein the subassembly composed of the core and the first stabilizing material, once it has been drawn comprises flat external surfaces upon which there are subsequently disposed the superconducting element (6) and intervening elements (14) of a material similar to the stabilizing material.
 11. A method as claimed in claim 1, wherein the material of the inner core portion is eliminated by melting.
 12. A method as claimed in claim 11, wherein the elimination of the material by melting, is assisted by the application of a gas pressure at one side, and the application of vacuum at the other.
 13. A method as claimed in claim 1, wherein the material of the inner core portion is eliminated by vaporizing.
 14. A method as claimed in claim 1, wherein the material of the outer core portion is eliminated by dissolving it in a solvent introduced into the space vacated by the elimination of the material of the inner core portion. 